Rapid Onset Relational Memory Effects Are Evident in Eye Movement Behavior, but Not in Hippocampal Amnesia

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Abstract
Little is known about the mechanisms by which memory for relations is accomplished, or about the time course of the critical processes. Here, eye movement measures were used to examine the time course of subjects' access to and use of relational memory. In four experiments, participants studied faces superimposed on scenic backgrounds and were tested with three-face displays superimposed on the scenes viewed earlier. Participants exhibited disproportionate viewing of the face originally studied with the scene, compared to other equally familiar faces in the test display. When a preview of a previously viewed scene was provided, permitting expectancies about the to-be-presented face to emerge, disproportionate viewing was manifested within 500-750 msec after test display onset, more than a full second in advance of explicit behavioral responses, and occurred even when overt responses were not required. In the absence of preview, the viewing effects were delayed by approximately 1 sec. Relational memory effects were absent in the eye movement behavior of amnesic patients with hippocampal damage, suggesting that these effects depend critically on the hippocampal system. The results provide an index of memory for face-scene relations, indicate the time by which retrieval and identification of these relations occur, and suggest that retrieval and use of relational memory depends critically on the hippocampus and occurs obligatorily, regardless of response requirements.